Electric coil consisting of a continuous strip-shaped conductor

ABSTRACT

An electric coil consisting of a continuous flat strip-shaped conductor wound together with one or more layers of an insulating material, adapted to insulate adjacent convolutions from each other and insulate the edges of conductive strip from contact with conductive elements in proximity to the coil.

United States Patent 1 1 Poulsen Nov. 6, 1973 [54] ELECTRIC COIL CONSISTING OF A 2,879,320 3/1959 Staley 336/192 X CONTINUOUS STRHLSHAPED 3,464,043 8/1969 Benko et a] 336/223 X 3,153,216 10/1964 Klitten 336/223 CONDUCTOR 2,735,979 2/ 1956 Cohen 336/223 X Peder Ulrik Poulsen, Esbonderup, 3230 Graest ed l)enmarl r Filed: Sept. 7, 1971 Appl. No.: 177,999

Inventor:

Foreign Application Priority Data Sept. 8, 1970 Denmark 4594 US. Cl 336/192, 29/605, 336/223, 336/232 Int. Cl H0lf 15/10, l-IOlf 27/28 Field of Search 336/222, 223, 192; 29/232, 605

References Cited UNITED STATES PATENTS 11/1970 Van Nice 336/223 X FOREIGN PATENTS OR APPLICATIONS 89,042 4/1936 Austria 336/223 Primary Examiner-Thomas J. Kozma Attorney-Eric l-I. Waters et al.

[5 7 ABSTRACT 3 Claims, 4 Drawing Figures ELECTRIC COIL CONSISTING OF A CONTINUOUS STRIP-SHAPED CONDUCTOR This invention relates to an electric coil consisting of a continuous flat strip-shaped conductor wound together with one or more layers of insulating material. The purpose of the latter is to insulate adjacent convulutions from each other and to insulate the edges of the metal strip from contact with conductive parts in the vicinity of the coil. The insulating material could be a separate film or an insulating layer attached to the conductor.

According to a much used procedure a comparatively wide strip is wound into an elongated coil which is thereafter cut into shorter units by means of knives that are pressed against the rotating coil. Normally coils made in this way are not immediately useable because burrs are often formed along the edges of the metal strip during the cutting thus short-circuiting adjacent turns and this calamity is met by a subsequent etching process wherein the individual coils are submerged completely or partly into an acid. Through this process possible burrs are removed along with the outermost edges of the metal foil so that the insulating film protrudes somewhat over the edges of the conductive strip whereby an effective insulation of the coil ends is secured.

According to a less complicated method the coils are wound one by one by using a strip of insulating film which is a little wider than the metal foil strip and winding the strips concentrically so that the insulating film is protruding over the edges of the metal strip thereby ensuring the above mentioned insulating effect.

No matter which method is used for the insulation of the coil ends it is very important that the strip materials are wound tightly to ascertain the mechanical stability of the coils and because compact and tightly wound coils have a better space factor and improvedresistance against intrusion of moisture from the coil ends. When the last described method is used wherein the coils are wound individually from strips having different widths it is of importance that the metal foil is cut without burrs because even in the case of a tightly wound coil the burrs will have a negative effect on the space factor. For this reason in some cases the metal strip is guided between a pair of flattening rollers. in continuation of the slitting process. I It is an object of the present invention to produce an electric coil by which the thickness of the strip-shaped conductor is varying along its length in regard of the required cross section area in each part of the coil. It is thereby obtained that the entire winding process can be made through a single operation and the cross section area will bekept as low as possible so that the dimensions of the coil will be kept at a minimum and thereby the electromagnetical properties of the coil will be most favourable.

A different problem in the making of strip wound coils is the making of reliable terminal connectors and possible intermediatetap leads. In coils with relatively large numbers of turns the metal foil is often thin and too weak to be used as a terminal connector itself and the litterature describes a large number of methods for the making of terminal leads and attaching these to the foil strip. When the material is copper it is a comparatively simple procedure to solder a wire or strip connector locally onto the conductor where a tap or terminal is required, but when aluminum foil is used it is difficult to get a reliable electrical contact by soldering due to the oxidation of the metal during the process. Accordingly, often mechanical methods are used for the attachment of terminal strips but as every joint is an inherent weakness their number is preferably reduced to a minimum.

In the cases when the only connectors in question are the terminals at the starting and finishing turns of the coil joints can be avoided by bending back the strip according to a 45 angle whereby the full width of'conductor can be taken out parallel to the coil axis. However, as mentioned, this technique is not satisfactory when the metal foil is very thin, and when the coils are wide the correspondingly wide terminal leads will often mean a disadvantage.

A further object of the present invention is to provide for a coil wherein the outlined difficulties are eliminated and by which tightly wound coils can be made from very thin foil and yet any number of mechanically strong taps and terminals can be carried out without introducing any joints at all. A still further object of the invention is to provide for a winding process which is rapid and free of soldering or welding operations. Further, the invention is related to an apparatus for carrying out the process. I

The invention will be described in the following with reference to the drawing, wherein FIG. 1 is the main elements of a winding apparatus for coils according to the invention, 7

FIG. 2, schematically, a strip conductor produced by unwinding a coil according to the invention,

FIG. 3 a detail of a tap lead from a coil according to the invention, and

FIG. 4 a modification of a tap lead.

The storage coil 1 contains metal foil having a width approximately equal to the width of the coil to be produced but substantially thicker than the thickness of the section of conductor required. For example the required cross section can be 5 mm needing a thickness of 0.1 mm or 2 mm which must be 0.04 mm thick. From the storage coil the strip is guided between two rollers 2 and 3 which are mounted rotatably in bearing blocks, not shown, and provided with an arrangement enabling the gap between the rollers to be varied and selected quickly and accurately anywhere within a range of for instance 0 to 1 mm. The roller 2 is fitted onto one of the output shafts of the gearbox 4 and roller 3 to the other output shaft via an arrangement of universal joints to allow for the above mentioned variation of the distance between the rollers. The gearbox 4 is connected with a motor, not shown, whereby the rollers can be brought into rotation with the same speed but in mutually opposed directions, as indicated by the arrows.

The bobbin 5 is fitted to the shaft of an electric torque motor 6 which could also be an over-running, torque adjustable coupling driven by a normal fixedspeed motor. The storage coil 7 contains insulating film, which is a little wider than the metal strip, and the arrangement is provided with an adjustable brake, not shown, by means of which the film tension can be adjusted within a suitable range.

The above components are arranged in such manner that the torque motor 6 tends to turn the bobbin in the direction indicated by the arrow, but as the roller gap is less than the thickness of the metal strip, the bobbin is prevented from turning unless the rollers are operating. The gearbox S is self-locking so that the rollers will only rotate when the drive motor is running and the HP of this motor is selected so that the rpm of the rollers may be governed, for example by means of a speed control device, without being affected appreciably by the tension in the strip due to the torque motor 6. On the other hand the torque provided by 6 must be enough to overcome the tension in the insulating film within its adjustable range. The effect of the above arrangement is that the rpm of the roller motor decides the winding speed, the torque yielded by the torque motor 6 decides the tension in the metal foil strip and the setting of the brake for the insulating film decides the tension of the film.

FIG. 2 illustrates a metal foil strip produced by unwinding a coil according to the invention and indicates how the mechanism is used during the winding process. When the procedure is started the roller gap is held at for example 0.4 mm for a moment and the starting end of the strip is thus reduced from 0.5 to 0.4 mm. Now the strip is slit as shown at 8 whereafter the narrow lead is bent free of the strip so that it protrudes from the coil parallel to its axis. Immediately thereafter the roller gap is reduced to the predetermined value, for example 0.04 mm and the first part of the coil is wound until point 10 is reached immediately prior to the desired tap where the gap is again raised to 0.4 mm while a length of strip sufficient for the tap lead is passing the rollers. The terminal is made like shown at 8 and the gap again reduced to 0.04 or for example 0.06 mm in case a larger cross section is required in the last part of the coil. Now the winding is continued till the gap is again raised to 0.4 mm at 12 and the coil completed with the terminal 13 prior to the normal banding with an insulating sheet.

FIG. 3 is a detail of the strip wherein the narrow lead has been stretched lightly at 14 by means of a hammer or by pressing with a special tool thereby bending the lead free of the strip until it is perpendicular to the tape axis. The advantage by this method is that a locally doubled thickness is avoided as it is the case when the strip is bent over as shown in FIG. 4. However, this version is normally faster to carry out and in some cases preferable.

By using the above described rolling-winding technique terminals from the first and final turn plus any number of taps in between can be made in a fast and simple procedure without joints along the way and thereby inevitable variations in quality. The cross sectional area of the terminal leads can easily be held larger than or equal to the conductor section in the rest of the coil and the comparatively narrow lead strips can be easily handled and due to their thickness clamped into connector blocks etcetera without particular caution. The terminals will have a good mechanical strength and it is often valuable that several different section areas can be used in the same coil without changes of strip during the winding. It is also an advantage that the necessary range of foil thicknesses held in stock can be reduced to a few, each of which representing a stepless range of conductor thicknesses.

What I claim is:

1. In an electric coil consisting of a flat strip-shaped conductor wound together with one or more layers of insulating material and containing two or more sections with taps or terminals, the thickness of the conductor being constant for each section and varying from section to section in accordance with the required cross sectional area in the section said taps or terminals and said conductor being of single unit construction in the sections of larger cross sectional area.

2. An electric coil in accordance with claim 1, said conductor having cut and outwardly bent parts along the edges thereof adapted to form taps and terminals, each part of the conductor in which a tap or terminal is formed being thicker than the adjacent conductor at least at one side of said part.

3. An electric coil in accordance with claim 1, said conductor having cut out and outwardly bent parts adapted to form taps and terminals, each part of the conductor in which a tap or terminal is formed being thicker than the adjacent conductor. 

1. In an electric coil consisting of a flat strip-shaped conductor wound together with one or more layers of insulating material and containing two or more sections with taps or terminals, the thickness of the conductor being constant for each section and varying from section to section in accordance with the required cross sectional area in the section said taps or terminals and said conductor being of single unit construction in the sections of larger cross sectional area.
 2. An electric coil in accordance with claim 1, said conductor having cut and outwardly bent parts along the edges thereof adapted to form taps and terminals, each part of the conductor in which a tap or terminal is formed being thicker than the adjacent conductor at least at one side of said part.
 3. An electric coil in accordance with claim 1, said conductor having cut out and outwardly bent parts adapted to form taps and terminals, each paRt of the conductor in which a tap or terminal is formed being thicker than the adjacent conductor. 